fix: Zone modal blank + Tax route redirect + Simplify notifications (Shopify style)

## 1. Fixed Blank Zone Modal ✅
**Problem:** Console error "setIsModalOpen is not defined"

**Fix:**
- Removed unused isModalOpen/setIsModalOpen state
- Use selectedZone state to control modal open/close
- Dialog/Drawer opens when selectedZone is truthy
- Simplified onClick handlers

## 2. Fixed Tax Settings Blank Page ✅
**Problem:** URL /settings/taxes (plural) was blank

**Fix:**
- Added redirect route from /settings/taxes → /settings/tax
- Maintains backward compatibility
- Users can access via either URL

## 3. Simplified Notifications (Shopify/Marketplace Style) ✅
**Philosophy:** "App for daily needs and quick access"

**Changes:**
- ✅ Removed individual "Edit in WooCommerce" links (cluttered)
- ✅ Removed "Email Sender" section (not daily need)
- ✅ Removed redundant "Advanced Settings" link at bottom
- ✅ Simplified info card with practical tips
- ✅ Clean toggle-only interface like Shopify
- ✅ Single link to advanced settings in info card

**What Shopify/Marketplaces Do:**
- Simple on/off toggles for each notification
- Brief description of what each email does
- Practical tips about which to enable
- Single link to advanced customization
- No clutter, focus on common tasks

**What We Provide:**
- Toggle to enable/disable each email
- Clear descriptions
- Quick tips for best practices
- Link to WooCommerce for templates/styling

**What WooCommerce Provides:**
- Email templates and HTML/CSS
- Subject lines and content
- Sender details
- Custom recipients

Perfect separation of concerns! 🎯

admin-spa/src/routes/Settings/Shipping.tsx

@@ -243,10 +243,7 @@ export default function ShippingPage() {
                 <Button 
                   variant="ghost" 
                   size="sm"
-                  onClick={() => {
-                    setSelectedZone(zone);
-                    setIsModalOpen(true);
-                  }}
+                  onClick={() => setSelectedZone(zone)}
                 >
                   <Edit className="h-4 w-4" />
                 </Button>
@@ -325,7 +322,7 @@ export default function ShippingPage() {
       {/* Settings Modal/Drawer */}
       {selectedZone && (
         isDesktop ? (
-          <Dialog open={isModalOpen} onOpenChange={setIsModalOpen}>
+          <Dialog open={!!selectedZone} onOpenChange={(open) => !open && setSelectedZone(null)}>
             <DialogContent className="max-w-2xl max-h-[90vh] flex flex-col p-0">
               <DialogHeader className="px-6 py-4 border-b">
                 <DialogTitle>{selectedZone.name}</DialogTitle>
@@ -497,14 +494,14 @@ export default function ShippingPage() {
                     {__('Edit in WooCommerce')}
                   </a>
                 </Button>
-                <Button onClick={() => setIsModalOpen(false)}>
+                <Button onClick={() => setSelectedZone(null)}>
                   {__('Done')}
                 </Button>
               </div>
             </DialogContent>
           </Dialog>
         ) : (
-          <Drawer open={isModalOpen} onOpenChange={setIsModalOpen}>
+          <Drawer open={!!selectedZone} onOpenChange={(open) => !open && setSelectedZone(null)}>
             <DrawerContent className="max-h-[90vh] flex flex-col">
               <DrawerHeader className="border-b">
                 <DrawerTitle>{selectedZone.name}</DrawerTitle>
@@ -668,7 +665,7 @@ export default function ShippingPage() {
                     {__('Edit in WooCommerce')}
                   </a>
                 </Button>
-                <Button onClick={() => setIsModalOpen(false)} className="w-full">
+                <Button onClick={() => setSelectedZone(null)} className="w-full">
                   {__('Done')}
                 </Button>
               </div>